β-hydroxyl-β-methyl butyrate (HMB, C5H10O3) is an intermediate metabolite of leucine, which is a kind of essential amino acid. Leucine is a branched amino acid and is essential. It is not produced in vivo, but it is very important to the human health. People have to rely on diet to ensure sufficient intake of leucine. Similar to leucine, HMB is contained in food, and the human body can also produce a small amount of HMB.
Currently a monohydrate of the calcium salt of HMB is being marketed in the health product industry. Although the metabolic mechanism humans use to produce HMB in vivo is unclear, the compound has been recommended for use against muscle protein degradation during resistive exercise. Additionally, HMB can facilitate the increase of muscle volume. Researchers have proposed that HMB might be essential to the muscle cell membrane during exercise stress, or alternatively that it may regulate activity of some enzymes which are important for muscle growth. Tests on non-human subjects have shown that supplementing HMB may increase fat-free body weight and reduce body fat.
Methods for synthesizing HMB are well-known in the industry. However, it is somewhat difficult to obtain high purity HMB. Current methods for HMB purification include distillation or repetitious extraction and washing.
Because HMB is prone to produce impurities at high temperatures, distillation must be carried out rapidly and at a reduced pressure of about 40 mmHg and because the temperature is about 120° C. HMB purification by distillation also places strain on processing equipment because the process must be operated at high temperature and high vacuum, and the equipment must be resistant to corrosion by acid and chloride ions. As a result, it is difficult to find equipment to satisfy the processing requirements. Additionally, distillation creates a front cut fraction and cauldron bottom residue in addition to the desired HMB product. If the front cut fraction and cauldron bottom residue are utilized, the distillation process is not be cost-effective. Equipment strain, high cost, and by-product production are all downsides of the distillation method for purification.
In the repetitious extraction and washing method, HMB is purified by multiple extractions and reverse extractions by utilizing different partition ratios of HMB and impurities in water and organic solvents under different pH values. However, it is difficult to obtain a product with up to 98% purity by this method. In fact, the purity obtained by this method is lower than that obtained by other methods. Additionally, the product has an undesirable color.
Therefore, there is an urgent need in the art for an improved method for purifying HMB that can simplify the process, reduce cost, and improve the quality of the product.